Traditional oral dosage drug formulations include both active pharmaceutical ingredients (API) and inactive ingredients. The inactive ingredients, also called excipients, are components of the final formulation of a drug that are not considered active pharmaceutical ingredients (API) in that they do not directly affect the consumer in the desired medicinal manner.
Traditional oral dosage forms have several inactive ingredients. Among the traditional inactive ingredients included in oral dosage forms are binders that hold the tablet together, coatings configured to mask an unpleasant taste, disintegrants configured to make the tablet break apart when consumed, enteric coatings, fillers that assure sufficient material is available to properly fill a dosage form, enhancers configured to increase stability of the active ingredients, preservatives aimed at preventing microbial growth, and the like.
Traditionally, the formation of an oral dose drug often included combining a desired pharmaceutical product with a number of the above-mentioned materials designed to control the release rate of the API when consumed. While the traditional method is effective for a number of soluble drugs, there are a number of highly water insoluble drugs that are not well suited to sustained or controlled delivery. The formulation of these highly water insoluble APIs into controlled or modified-release dosage forms using traditional formulation methods is both expensive and challenging due to the APIs insolubility and unknown stability.
Microemulsion formulations potentially offer a variety of desirable properties for pharmaceutical delivery, namely, high solubility, high absorption, and improved pharmacokinetics. However, precise dispensing and distribution of the microemulsions formed for pharmaceutical product delivery has proven to be somewhat problematic as noted in the following publications: Using microemulsions for drug delivery, Pharmaceutical Technology, 1987; Improved drug delivery using microemulsions: Rationale, recent progress, and new horizons, Critical Reviews in Therapeutic Drug Carrier Systems, 2001; and Microemulsions: an overview and pharmaceutical applications, Critical Reviews in Therapeutic Drug Carrier Systems, 1999.